What sticks in my head is the fact that Canon very likely knew how this worked months before it was officially released. This camera has been in development and field testing for years. They are likely seeing some kind of spike in return/repair rates for the same AF problem. If I just returned mine, 1000's of others have got to be returning theirs or having Canon check them at a repair center. Most buyers of this level camera are going to know how to use the thing so Canon shouldn't expect that the problem won't be noticed. Esp when the low light features are so heavily marketed. So what gives?? I know my camera had to have a problem, even if it's a design problem across the board. But I trust the professional I know that owns two 5D3's and says she loves them and hasn't had any problems at all. She isn't a fan-girl, all she cares about are the images. So is the Canon QC/QA so poor that some bodies work great while others don't? And why hasn't lensrentals.com said anything about it? You would think with all the 5D3 rentals they do, they would have received plenty of complaints as well. No mention of that, that I know of anyway. So I'm holding out a tiny ray of hope that the next camera that shows up will be untouched brand new, undamaged during shipment and work perfectly in all respects.

All I know for sure is that as I do post processing on a lot of images I shot recently with my 5Dc I am still blown away with the quality that comes out of that camera. And they didn't cost $3000+ to make!

Depending on what I discover with the second copy of the 5D3 body when I receive it hopefully next week, I guess the 6D may become the 'last hope' Canon camera for significant low light AF performance. And if the 6D DOES focus significantly faster and better than the 5D3, I think we are going to see a lot of pissed off 5D3 owners! I don't even want to think about what the 1DX owners will do!

I do not understand why it takes so long for the focus indicator to light, but since I get in-focus shots quickly by just holding and pressing the shutter, thats what I do.

This thread is getting a little confusion because the title is about af assist but now it's about low light af in general... the fix "just full-press the shutter" is valid for shots with flash and af assist, too?

Yeah some people are mixing up the issue at hand here.The AF of the 5D3 is outstanding, even in super low light (near darkness) situations. It hits fast and accurate!BUT, if you use a flash with the AF assist beam on in low light situations. It sucks. And that is the problem, which is quite frustrating.

I did notice those problems with my 5D3 and a 580EXII flash. It just takes too long to focus.

I tried 580EXII with my 7D and noticed that the assist beam was bigger, lighter.. well, there is really a difference in the beam.

I think if you try to focus on further (and by further I mean about 3 meters) the assist beam it's not so effective. I say this because I tried to focus on a close object in an almost dark environment and it was ok.

I have been considering trading one of my 5D mark 2's for a Mark 3 lately, but im definitely not going to pull the trigger on it for a while after reading all these problems, as I use my 580 flash extensively at my Weddings and I foresee this really annoying me. I wonder if 1Dx owners are experiencing this problem as well?

Thanks for spending time on this Northstar! I'm looking forward to receiving the replacement camera and hopefully seeing better performance. It helps to have someone else to compare with.

Since I shoot in both normal indoor and darker indoor/outdoor areas using my older cameras, esp the old trusty 5Dc, I'm comparing to those with regard to what is already normal for me and achievable with older technology. If the 5D3 can't improve on that in the same circumstances or performs worse, than I have to assume either the camera is faulty, everyone is lying or it has a design flaw. What else can I assume, right? I suspect a little bit of everything is possible. I know how to manage my expectations, but what I (and others) have experienced sounds ridiculous.

I've already got the good glass. Canon marketing, various reviews and some other individuals attest that the 5D3 is a miracle camera. So I guess I just want the miracle dammit!

Thanks again!

You must have had a bad copy...again, theses shots I took were 25 minutes after sunset and it was almost pitch dark out....no problems locking on focus in "available low light shooting"

Thanks for spending time on this Northstar! I'm looking forward to receiving the replacement camera and hopefully seeing better performance. It helps to have someone else to compare with.

Since I shoot in both normal indoor and darker indoor/outdoor areas using my older cameras, esp the old trusty 5Dc, I'm comparing to those with regard to what is already normal for me and achievable with older technology. If the 5D3 can't improve on that in the same circumstances or performs worse, than I have to assume either the camera is faulty, everyone is lying or it has a design flaw. What else can I assume, right? I suspect a little bit of everything is possible. I know how to manage my expectations, but what I (and others) have experienced sounds ridiculous.

I've already got the good glass. Canon marketing, various reviews and some other individuals attest that the 5D3 is a miracle camera. So I guess I just want the miracle dammit!

Thanks again!

You must have had a bad copy...again, theses shots I took we're 25 minutes after sunset and it was almost pitch dark out....no problems locking on focus in "available low light shooting"

I disagree. I don't think it is a bad copy or malfunctioning body. A lot of 5D3 users have this phenomenon shooting in certain conditions (Nightclubs, dark wedding receptions etc where flash is required). Shooting in low light without flash is not the problem at all, in fact this works perfect. Fast, accurate and very responsive and a hell of fun! The problem is locking focus with the AF assist Beam with the Speedlights attached in low light situations. That is where the "lag" happens, even with a fast lens!

Now compare this with the AF system of the 5D2. This ancient AF was practically blind on that body in dark situations without the flash AF Assist. Engage the AF Assist and it became a fast focusing eagle in pitch black situations. The 5D3 just can't do this with its "Pro-AF" and that's where the frustration comes from.

Another factor should be taken in account with this AF Assist problem on the 5D3. Distance. When you are really close to the subject the lag is not very noticeable (around 1m). When the distance is somewhere in the "portrait" range than you'll notice it. Moving subjects can make a difference as well. But in comparison the 5D2 is much much faster in the same conditions.

I did notice those problems with my 5D3 and a 580EXII flash. It just takes too long to focus.

The really surprising issue is that even with the new 600rt flash which is the same product generation this problem seems to occur - and Canon adjusted the af assist to match the 1dx/5d3 af spread, so if they didn't fix it then they probably simply aren't able to.

Since this is an issue affecting many pros it would be nice to get some first-hand information from Canon, their pro support is said to be good and responsive to the customers?

Yeah some people are mixing up the issue at hand here.The AF of the 5D3 is outstanding, even in super low light (near darkness) situations. It hits fast and accurate!BUT, if you use a flash with the AF assist beam on in low light situations. It sucks. And that is the problem, which is quite frustrating.

The low/available light AF Lock has never been fast enough for me, regardless of whether or not the AF Assist is enabled/disabled or the flash is present or not. So I thought that might be relevant to the topic even if it didn't match the hypothesis or original poster's results exactly. Sorry if it took the thread off topic. I thought slow AF Lock malfunction was the underlying topic and the AF Assist beam setting was the fix. So I addressed the problem and noted the fix didn't work for me. Therefore, AF is somewhat broken for me, and that's how the topic drifted. Sorry. Whatever the case, I got enough consensus to determine I should try returning my copy and hope for a better copy next week. So thanks for that everyone!

And I find it disconcerting that the fix for bad low light AF performance is to disable a key feature to trick the camera into working correctly. Who goes to a dark shooting environment with no flash attached so they will have a better chance of pictures being in focus but possibly too dark to use? So now instead of having the subjects wait 3-4 seconds for the AF Lock to work with the flash attached, I have to have them wait even longer while I detach or attach the flash and fumble with it or change a menu setting before I can take the shot. Hmm. Sounds like a great work around to me. Thanks Canon! I guess the reality is that we're back to manual focus again.

Sorry. Whatever the case, I got enough consensus to determine I should try returning my copy and hope for a better copy next week.

I am amazed that this issue pops up now after so much time - maybe people are just now realizing that it's the camera's and not their fault? In any case I don't understand why switching 5d3 copies should solve anything, either the firmware/camera/flash-combination has broken low-light af or it hasn't. Go, 6d, go :-p

So now instead of having the subjects wait 3-4 seconds for the AF Lock to work with the flash attached, I have to have them wait even longer while I detach or attach the flash and fumble with it or change a menu setting before I can take the shot.

I guess turning the flash off should suffice - isn't it? Maybe even turning off the af assist feature in camera and disabling the flash to fire (on the 600rt, that's a dedicated button).

The 6D may only have one center cross-type AF point, compared to the 41 cross-type points on the 5D3′s AF system, but Westfall actually said that AF speed on the 6D could potentially outperform the 5D3 in low-light situations using that single cross-type. Westfall said that the 6D should be on par with the 5D3 at lower ISOs, but should outperform at higher ISOs, thanks to larger pixels on the full-frame sensor.

Sorry. Whatever the case, I got enough consensus to determine I should try returning my copy and hope for a better copy next week.

I am amazed that this issue pops up now after so much time - maybe people are just now realizing that it's the camera's and not their fault? In any case I don't understand why switching 5d3 copies should solve anything, either the firmware/camera/flash-combination has broken low-light af or it hasn't. Go, 6d, go :-p

So now instead of having the subjects wait 3-4 seconds for the AF Lock to work with the flash attached, I have to have them wait even longer while I detach or attach the flash and fumble with it or change a menu setting before I can take the shot.

I guess turning the flash off should suffice - isn't it? Maybe even turning off the af assist feature in camera and disabling the flash to fire (on the 600rt, that's a dedicated button).

Don't be amazed. The issue will continue to pop up until it doesn't exist. I am switching copies because others seem to not have the problem to the extent I think I do. After using the 2nd copy, I'll decide whether or not to dump the 5D3 or keep it. And I totally agree, the 6D very well might be the fix, esp for what I do. I was going to buy the 6D in the first place but got a great deal on the 5D3 so I figured why not? It's 'new camera time' either way. I turn my flash on/off all the time. I was referring to the comments that spoke to physically removing the flash instead of just powering it off to fix the problem. And I disabled the AF Assist right away after I read that fix. Not much of a change for me, still poor low light AF Lock. I work hard to be objective and not let the fancy new camera convince me that it must just be me. It's just a tool. I like to think I'm the one with the brain, as scary as that sounds.

As much as I like some of the features of the 5D3, I actually hope the 6D is better for me, I'll save several hundred dollars and probably make a profit on selling my 5D3 because of the good deal I got. (For me, the camera isn't bling, it's the next accidentally broken expensive tool I might have to replace someday.) I just hope the 6D isn't delayed over and over like Canon is so well known for.

I wonder if some of them frequent this web site but can’t say anything

First, real quick, what is UAT? I'm missing it, sorry. Thanks.

So would I!! I think this all the time! Every time I ask the question, "Gee, did anyone actually use this piece of sht when they were designing it???" with regard to many things I've owned over the years, not just cameras. I think that's the reason cameras are so good for the most part, they are very heavily tested and used to determine what features, ergonomics, etc will actually work best. A lot more so than just about any other item I buy.

Whoever is granted the chance to beta test pre-release cameras I'm sure are buried in NDAs and I'm sure they are more than competent to perform the task. They submit their findings and Canon does what they want with them. It can't be any other way. I'm sure the competition would love to get pre-release copies and would pay well for them. So the beta testers are likely very good, very loyal and very discreet.

IMO, there is no way Canon doesn't know about every microscopic detail of this camera as the development proceeds. At the end of the day they released it as it is (after they probably delayed as long as they could) and assume they can continue to fix and improve it after that time with the public's real world testing as a further guide. Canon is likely working with concurrent development timelines of products, not individual product development. We are part of that timeline. This is why I prefer to wait 6-9 months before I buy a new camera, I don't want to be part of the initial bleeding edge beta testing for Canon and pay the high release price for the privilege. At the end of the day, Canon is a business out to make money, not make perfect cameras. When they reach a certain point in the development timeline, it's time to release, period. Because they lose money every week they delay. I'm not saying they didn't delay release, I'm saying eventually they can't delay any longer and if the problems can't be fixed, they'll try to fix them later and let us use them as-is until that time. They are NOT going to scrap the entire project or delay indefinitely just because it doesn't work like we think it should. They probably went too far in development of the AF system to turn back when they realized the low light AF wasn't what they expected from the design. So, quick(!), take that other design we were working on and create the 6D!! And if I'm right, buying a 6D at release time will hopefully result in fewer bugs than usual because the tech in it has already been tested to death in the 5D3 and 1DX and it was merely tweaked and modified in the 6D and put in a different shell. In 6 months, we might be saying that the serious wedding photographer should carry both the 6D for low light and the 5D3 for all other IQ stuff. Fingers crossed....